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Howlett" , David Hildenbrand , "Matthew Wilcox (Oracle)" , Brendan Higgins , David Gow , damon@lists.linux.dev, linux-mm@kvack.org, kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/tests/vaddr-kunit: init maple tree without MT_FLAGS_LOCK_EXTERN Date: Wed, 4 Sep 2024 11:53:47 -0700 Message-Id: <20240904185347.2253-1-sj@kernel.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <34f3e9bd-9323-43cc-8371-00d8847d8664@roeck-us.net> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DD75814000A X-Stat-Signature: bfn6jo1w5p6gbjmbzqkownko7b7mywbf X-Rspam-User: X-HE-Tag: 1725476032-533396 X-HE-Meta: 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 ir8IHLtc X/QxFvT0Aw8F1x5Ym0zMpX0DyyMp4nHKdqHfXy+97M72qS81ezadVQfi1ppmEbSfubrbrbuAaJx+QLvyelm0Dd/GGd+MJ+Yj1o7L9jByQSR+PNGxeXQTucNM/msXipXCexKjwoWB22/bXQvgI06oEnNjzk/ceEZPvjcEG/RrxjtSpVgWjHKZnol1iQL7RLU3wLFt2ss0aq0Sj21SzExbhWlcp1BuI8EHpPrlU9SOV1q1R91vrz/cZpS25saD/nY1oHYNyoZjJFhXrz5JrmgGC0DfVsm74Hpo9sTXxU/oxGrdGhtWp3lnkZAQE//XlXxtLpQ1XoFzy7hmlReC1vUud1S5Ckk9lGu+tswl3vY8budUsSM8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 4 Sep 2024 11:41:28 -0700 Guenter Roeck wrote: > On 9/4/24 10:29, SeongJae Park wrote: > > damon_test_three_regions_in_vmas() initializes a maple tree with > > MM_MT_FLAGS. The flags contains MT_FLAGS_LOCK_EXTERN, which means > > mt_lock of the maple tree will not be used. And therefore the maple > > tree initialization code skips initialization of the mt_lock. However, > > __link_vmas(), which adds vmas for test to the maple tree, uses the > > mt_lock. In other words, the uninitialized spinlock is used. The > > problem becomes clear when spinlock debugging is turned on, since it > > reports spinlock bad magic bug. > > > > Fix the issue by excluding MT_FLAGS_LOCK_EXTERN from the maple tree > > initialization flags. Note that we don't use empty flags to make it > > further similar to the usage of mm maple tree, and to be prepared for > > possible future changes, as suggested by Liam. > > > > Reported-by: Guenter Roeck > > Closes: https://lore.kernel.org/1453b2b2-6119-4082-ad9e-f3c5239bf87e@roeck-us.net > > Fixes: d0cf3dd47f0d ("damon: convert __damon_va_three_regions to use the VMA iterator") > > Suggested-by: Liam R. Howlett > > Signed-off-by: SeongJae Park > > --- > > Changes from v1 > > (https://lore.kernel.org/20240904004534.1189-1-sj@kernel.org) > > - Keep lock usage and update the initialization flags (Liam) > > Not sure I understand how this is better. Is the resulting rcu warning > considered to be irrelevant or a separate problem ? I believe it's a separate potential problem (warning) that deserves a look. Meanwhile, this patch is fixing an issue that is definitely a bug, so better to fix right now, imho. Thanks, SJ [...]